The reigning champions have lost five of their six matches after another battling capitulation against India on Sunday, leaving them rooted to the bottom of the 10-team table.
England restricted the tournament hosts to a modest 229-9 but imploded in their chase and were all out for 129 inside 35 overs.
"Very disappointing," Butter said after the 100-run thrashing left them with only mathematical chances of making the last four.
"At the halfway stage chasing 230, we fancied ourselves. But it's the same old story."
England face Australia, the Netherlands and Pakistan in their remaining matches and a only a top-eight finish would guarantee them a place in the Champions Trophy in Pakistan.
"Yeah, we are aware of that and absolutely, we've still got lots to play for," Buttler said.
The stumper-batsman was pleased with their bowling and fielding and lamented how poor batting let them down again.
"We were excellent in the field. We made a great start in the powerplay.
"Players found some movement, bit of indifferent bounce and the ground fielding has been as good as its been. So it felt like today was the day it turned around. But the way we batted didn't back that up."
Asked to explain England's underwhelming performance in the tournament, Buttler said, "Answers on a postcard. There's some top players in there and we were a long way short of their best."
Additional reporting by Reuters.